Spin drive motor for a disk storage device

ABSTRACT

A disk storage drive for a disk storage device having a clean chamber for a storage disk having a central opening is provided with a brushless drive motor. The drive motor includes a stator and a winding on the stator and further includes a shaft aligned with the rotation axis of said motor, and a magnetically conducting member supported for rotation about the rotation axis and having an inner wall coaxially surrounding the stator. A magnet fixed to the inner wall of the magnetically conducting member is radially spaced from the stator. The disk storage device further includes a hub positioned within the clean chamber and contiguous with the magnetically conducting member so that the hub and the magnetically conducting member together form an outer rotor of the drive motor. The outer rotor has a radially extending flange having a surface which supports said storage disk. A support member contiguous with a portion of a partition of the clean chamber supports the shaft and has a recess receiving a portion of said radially extending flange, whereby the spacing between opposing walls of the clean chamber is reduced. Further, the magnetically conducting member comprises magnetic shield means at least peripherally surrounding the stator and at one end radially extending to the bearing and shaft assembly, and the rotor has a radially extending inner wall spaced closely adjacent to said stator windings, whereby said disk storage device is compact in a direction along said disk rotation axis while said motor magnet is axially separated from the plane of said storage disk.

This application is a continuation of application Ser. No. 08/227,645filed Apr. 14, 1994 (U.S. Pat. No. 5,422,769, Jun. 6, 1995), which is acontinuation of application Ser. No. 08/047,308 filed Apr. 19, 1993(U.S. Pat. No. 5,446,610, Aug. 29, 1995), which is a continuation ofapplication Ser. No. 07/883,478 filed May 15, 1992 (U.S. Pat. No.5,216,557, Jun. 1, 1993), which is a continuation of application Ser.No. 07/682,495 filed Apr. 9, 1991 (U.S. Pat. No. 5,128,819, Jul. 7,1992), which is a continuation of application Ser. No. 07/259,132 filedOct. 18, 1988 (U.S. Pat. No. 5,006,943, Apr. 9, 1991), which is acontinuation of application Ser. No. 07/032,954 filed Mar. 31, 1987(U.S. Pat. No. 4,779,165, Oct. 18, 1988, now U.S. Pat. No. RE 34,412,Oct. 19, 1993), which is a continuation of application Ser. No.06/733,231 filed May 10, 1985, abandoned, which is acontinuation-in-part of application Ser. No. 06/412,093 filed Aug. 27,1982, abandoned.

BACKGROUND OF THE INVENTION

The invention relates to a disk storage drive for receiving at least onestorage disk having a central opening, with an outer rotor type drivingmotor having a rotor casing mounted by means of a shaft in a bearingsystem so as to rotate relative to a stator and on which can be placedthe storage disk for driving by the rotor casing, as described in U.S.patent application Ser. No. 353,584, now U.S. Pat. No. 4,438,542, issuedMar. 27, 1984.

The content of this patent is incorporated herein by reference to avoidunnecessary repetition. It relates to a disk store and storage drive forreceiving at least one storage disk having a central opening. Thedriving motor extends coaxially at least partly through the centralopening of the storage disk, and means are provided for connecting thestorage disk and the driving motor rotor.

BRIEF SUMMARY OF THE INVENTION

The problem of the present invention is to further simplify theconstruction of a disk store described in the aforementioned U.S. Pat.No. 4,438,542, while improving its operation. In particular, the storagedisk is to be reliably protected against undesired influencing by themagnetically active parts of the driving motor. In addition, aparticularly space-saving and robust construction of the driving motorare to be achieved.

According to the invention, this problem is solved in that at least thepart of the rotor casing receiving the storage disk is made from anon-ferromagnetic material and carries the shaft directly or by means ofa hub and in that a magnetic shield made from a ferromagnetic materialin the form of a drawn can projects into the storage disk receiving partof the rotor casing and is connected thereto. The shielding surroundsthe periphery of the magnetically active parts of the driving motor andalso envelops the parts at one end. The shield has a central openingwhose edge is directly radially adjacent the shaft or parts of thedriving motor carrying or supporting the shaft. A rotor casingconstructed in this way can be easily manufactured, and it effectivelyprotects the magnetically sensitive storage disks, particularly magnetichard storage disks, against magnetic stray flux emanating from themagnetically active parts of the driving motor. The shield is preferablyin the form of a deep-drawn can, and the part of the rotor casingreceiving the storage disk can be made for a lightweight metal by diecasting.

If, in the manner described in the aforementioned U.S. Pat. No.4,438,542, the driving motor is constructed as a brushless directcurrent motor with a permanent magnet rotor, then in accordance with afurther development of the invention a printed circuit board with atleast one rotary position detector and perhaps other electroniccomponents for the control and regulation of the driving motor aremounted on the side of the stator remote from the bottom of theshielding can. This ensures that the rotary position detector and anyfurther circuit components of the magnetic shielding arrangement do notinterfere with the rotating parts.

Further advantageous developments of the invention also are disclosed,including features that contribute to a compact construction of the diskstorage drive. In connection with disk storage drives of the presenttype, high demands are made on the concentricity of the storage disks.It is therefore generally necessary to machine the storage diskreceiving part or to work it in some other way so that it isdimensionally true. As a result of other features of the invention, thenecessary machining is reduced to a relatively small part of thecircumferential surface of the storage disk receiving part and atrouble-free engagement of a storage disk on the shoulder of the storagedisk receiving part is permitted.

Other features of the claimed invention provide a robust precisionmounting support for utilizing the available axial overall length formaximizing the distance between the bearings; and permit particularlylarge distances between the bearings where the axial installation areabetween a mounting or assembly flange and the end of the storage diskreceiving part is limited. Installation space is available on the otherside of this flange. Still other features provides for alternativesolutions leading to particularly small radial runouts of the rotor;ensure a space-saving housing of the circuit board; and for solutionswhere importance is attached to a particularly shallow construction.

BRIEF DESCRIPTION OF THE DRAWINGS.

The invention is described in greater detail hereinafter relative tonon-limitative embodiments and the attached drawings, wherein:

FIG. 1 is a vertical partial sectional view through a first embodimentof the invention along the line I--I of FIG. 2;

FIG. 2 is a plan view of the arrangement of FIG. 1;

FIG. 3 is a sectional view through another embodiment of the inventionwith an extended bearing tube;

FIG. 4 is a sectional view through a further embodiment of theinvention;

FIG. 5 is a section through a disk storage drive according to theinvention along line V--V of FIG. 6;

FIG. 6 is a diagrammatic section along line VI--VI of FIG. 5;

FIG. 7 is a section similar to FIG. 6 for a modified embodiment;

FIG. 8 is an axial section through a disk storage drive according to afurther modified embodiment of the invention;

FIG. 9 is an axial partial section for a further modified embodiment;

FIG. 10 is an axial partial section for an embodiment with a magneticyoke ring and separate axial shield ring;

FIG. 11 is an axial partial section through a further modifiedembodiment of a disk storage drive with a fixed shaft; and

FIG. 12 is a partial section corresponding to FIG. 11 for an embodimentwith a fixed shaft.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.

The disk storage drive illustrated in FIG. 1, having an extremelyshallow construction, has a brushless direct current motor 45 having arotor casing 47 fixed to and coaxial with a rotor shaft 46. A statorlamination 48, carrying a stator winding 49, is mounted on a bearingtube 50. The rotor shaft 46 is rotatably mounted within the bearing tube50 by means of two bearings 52 and 53. These are kept axially spaced bya pair of retaining rings 54. A cup spring 55 is supported on theunderside of the bearing 53 by a retaining ring 56 resting on the rotaryshaft 46, so that the bearings 52, 53 are axially braced relative to oneanother. The bearings 52, 53 are pressed into the bearing tube 50 at thetime of assembly. Together with an assembly flange 24, the bearing tube50 forms a one-piece die casting.

The rotor casing 47 comprises a storage disk receiving part 25 and ashielding can 26, which are joined together, for example, by riveting.The storage disk receiving part 25 commonly known as a hub, is made froma non-ferromagnetic material, preferably lightweight metal. The rotorshaft 46 is pressed into a central opening of the storage disk receivingpart 25. As an alternative, the shaft can be cast into the receivingpart.

The shielding can 26 is made from a ferromagnetic material and can inparticular be constructed as a soft iron deep-drawn part commonly knownas a soft magnetic annular yoke. A plurality of permanent magneticsegments or a one-part permanent magnet 69 are fixed to the inner faceof shielding can 26 radially facing the stator lamination 48 and definethe diameter of the substantially cylindrical air gap with respect tothe stator lamination 48. The permanent magnet 69 preferably comprises amixture of hard ferrite, for example, barium ferrite, and an elasticmaterial. Thus, it is a so-called rubber magnet. The latter istrapezoidally or approximately trapezoidally radially magnetized via thepole pitch in a motor construction having a relatively small poleclearance. At the same time, the shielding can 26 forms the magneticreturn path for magnet 69. The shielding can 26 surrounds themagnetically active parts 48, 49, 69 of the driving motor 45 on theperiphery thereof, as well as on one end thereof. The bottom 28 ofshielding can 26 is adapted to the shape of the coil winding heads 27 ofthe stator winding 49 and contains a central opening 29, whose edge isin the immediate radial vicinity of the circumferential surface of thebearing tube 50 and has a diameter less than the diameter of bearing web80. In this way, the shielding can effectively prevents the magneticflux from straying towards the outside of the storage disk receivingpart 25.

The storage disk receiving part 25 has two stepped stages 74 and 75,each of whose circumferential surfaces in the present embodiment carry aplurality of radially distributed and projecting bearing webs 79 or 80.The outsides of bearing webs 79, 80 the disk bearing surfaces, areground in a dimensionally true manner to accommodate the internaldiameter of the hard storage disks to be placed on the receiving part25. The smaller of these opening diameters, for bearing web 80, is lessthan the air gap diameter. The stepped stages 74, 75 form shoulders 81,82 and are provided respectively with an annular recess 83 and 84 at thefoot axially of bearing webs 79, 80. This structure ensures that storagedisks mounted on the bearings webs 79, 80, and having either one of twoopening diameters, will cleanly engage against either the shoulder 81 or82.

The assembly flange 24 is provided with a recess 85 in which is housed aprinted circuit board 86. This printed circuit board carries a rotaryposition detector, for example a Hall IC, as well as other circuitcomponents for the control and regulation of the driving motor 45. TheHall IC 63 extends up axially from the circuit board 86 to the immediatevicinity of the stator lamination 48. The permanent magnet 69 projectsaxially over the stator lamination 48 in the direction of circuit board86 until it partly overlaps the Hall IC 63. In this way, the Hall IC 63or, if desired, some other magnetic field-dependent semi-conductorcomponent, determines the rotary position of the rotor of the drivingmotor 45.

In the illustrated embodiment, the two bearings 52, 53 are spacedapproximately the same axial distance from the axial center of thepermanent magnet 69 and the stator lamination 48.

Disk storages are most usually operated in "clean room" environments toprotect them against contaminants. By means of the assembly flange 24,the storage drive is arranged on a partition (not shown) which separatesthe ultra-clean area for receiving the storage disks from the remainderof the interior of the equipment. Dirt particles, grease vapors and thelike from bearing 52 and parts of the driving motor 45 are preventedfrom passing into the storage disk receiving area by labyrinth seals 90and 91. The labyrinth seal 90 is formed in that the end of the bearingtube 50 away from the assembly flange 24 that projects into an annularslot 87 on the inside of the storage disk receiving part 25, accompaniedby the formation of sealing gaps. Similarly, for forming the labyrinthseal 91, the end of the shield can 26 projects into the annular slot 88of the assembly flange 24. The annular slot 88 is formed in part by anouter portion of assembly flange 24 and has inner and outer diametersaccommodating the edge of shielding can 26 and its respective inner andouter diameters. The labyrinth seals 90, 91 are preferably dimensionedin the manner described in the aforementioned U.S. Pat. No. 4,438,542.

The embodiment of FIG. 3 differs from the arrangement according to FIGS.1 and 2 in that storage disks having the same opening diameters areplaced on bearing webs 79 of a storage disk receiving part 89, whichsurrounds the majority of the axial dimension of the magnetic shieldingcan 26. In other words, the magnetically active parts 48, 49, 69 of thedriving motor 45 are partially located within the central opening of thestorage disk. A bush-like hub 98 is pressed or cast into the storagedisk receiving part 89. The rotor shaft 46 is then pressed into the hub98. The edge of the central opening 29 in the bottom 28 of the shieldingcan 26 extends up to the portion 99 of the receiving part 89 whichreceived the hub 98.

The bearing tube 50 projects in the axial direction on the side of theassembly flange 100 remote from the stator lamination 48. As a result, aparticularly large axial spacing between the two bearings 52, 53 can beachieved. Axially, bearing 52 is in the vicinity of the axial center ofthe permanent magnet 69 and of the stator lamination 48. The axialspacing between bearings 52 and 53 is equal to or larger than double thebearing external diameter. To prevent electrical charging of the rotorwhich in operation rotates at high speed and which would disturb theoperational reliability of the disk storage device, the rotor shaft 46is electrically conductively connected to the equipment chassis by meansof a bearing ball 78 and a spring contact (not shown). The printedcircuit board 101, carrying the rotary position detector 63 and theother electronic components, is supported on the and of a spacer ring102 facing an assembly flange 100 and is located between the flange andthe stator lamination 48. An annular slot 103 is formed in assemblyflange 100 and is aligned with the annular circuit board 101. Theannular slot 103 provides space for receiving the wire ends and solderedconnections projecting from the underside of the circuit board 101.

FIG. 4 shows an embodiment in which a storage disk receiving part 105 isaxially extended in order to be able to house a larger number of storagedisks than in the arrangement of FIG. 3. The bearing tube 50 iscorrespondingly axially extended in order to be able to use the existinginstallation space with a view to a maximum axial spacing between thebearings 52 and 53.

The end of the bearing tube 50, remote from as assembly flange 106,embraces the hub 98 connecting the receiving part 105 and the shaft 46,accompanied by the formation of a labyrinth seal 107. The edge of thecentral opening 29 of shielding can 26 extends up close to the outsideof the bearing tube 50. The free end of the shielding can 26 engages arecess 108 in the assembly flange 106. As a result, a further labyrinthseal 109 is formed. This embodiment otherwise corresponds to thestructures described hereinbefore.

In a further development of the invention where a disk storage driveutilizes a brushless D.C. drive motor having a stator provided with awinding and an external rotor coaxially surrounding the stator andspaced therefrom by a substantially cylindrical air gap, the rotorincluding a permanent magnetic rotor magnet and a soft magnetic yoke.The motor further includes a hub concentric to the yoke and connected tothe rotor for rotation therewith. The hub is a disk mounting or supportportion, which extends through the central opening of the storage diskand receives at least one storage disk in a clean area space, or chamberof a storage drive.

In known disk storage drives of this type there is a hub or armaturesleeve for receiving the storage disk or disks wherein the disk mountingportion extends over a small part of the axial dimension of themagnetically active stator and rotor parts, i.e. the stator winding andthe rotor magnet that interacts therewith.

In disk storage units, there is an increasing need for reducing thespace requirement for the storage unit. Thus, another problem of theinvention is to provide a disk storage drive that takes up particularlylittle space and consequently allows a minimization of the disk storagedimensions.

According to a further aspect of the invention, this problem is solvedby the stator winding and the rotor magnet interacting therewith, atleast with respect to half their axial dimension, being housed withinthe area surrounded by the disk mounting portion of the hub. Themagnetically active parts of the drive motor in this construction arelocated mostly within the space which is already required for holdingthe storage disks, particularly magnetic rigid storage disks, but alsostorage disks of other types, e.g. optical storage disks.

Preferably, the stator winding and the motor magnet interactingtherewith are contained within the space surrounded by the disk mountingportion of the hub by up to 2/3 of their axial dimension. A particularlyspace-saving overall arrangement is obtained if the magnetically activestator and rotor parts are located substantially completely within thisspace.

The diameter of the central opening of the storage disks, e.g. magneticrigid storage disks, is standardized and consequently its size ispredetermined by industry and the market to a fixed value. However, theapplication of the drive energy requires a certain motor size. Theconditions are particularly critical in known small storage disks with acentral opening diameter of, for example, only 25 mm. In order toprovide maximum space for the magnetically active motor parts in thediametrically limited area of the storage disk central opening,according to even a further development of the invention, the wallthickness of the disk mounting portion of the hub is minimizedconsistent with needed mechanical strength. The wall thickness of thedisk mounting portion is appropriately the same as and preferablysmaller than the wall thickness of the part of the magnetic yoke whichis concentric thereto.

The disk mounting portion preferably has a cylindrical outer peripheralsurface, that is, a peripheral surface free from bearing webs or ribs inproviding a maximum cross section while taking into account the fixeddiameter of the central opening of the storage disks consistent with thenecessary mechanical strength of the hub.

At least those surface parts of the hub located in the clean area orchamber of the drive must not give off, even during prolonged use of thedisk storage drive, significant quantity of dirt particles, for example,from oxidation. Preferably, the hub is made from a material which, evenafter cutting, is suitable for use in a clean area or chamber, that is,a material which after being cut, and without a corrosion-inhibitingtreatment following the cutting, meets the strict cleanness conditionsnecessary with disk storage drives in the clean chamber of the drivesreceiving the storage disks. Such a construction makes it possible tofinish, for example, by grinding or otherwise stripping the outerperipheral surface of the disk support portion after assembly of the huband the drive motor with respect to the centricity with the rotationaxis. Such metal finishing of the installed hub is frequently necessaryin order to fulfil the extreme demands in connection with disk storagedrives with respect to accuracy of rotation or minimization ofuntrueness of the hub. It is particularly appropriate to have a hub madefrom light metal, preferably aluminum or an aluminum alloy. Light metalhubs can be used in clean chambers without further treatment, even aftercutting has taken place. For example, by using a diamond tool, and whilerespecting the necessary precision, such hubs can be stripped in a lessexpensive way than by grinding, particularly the disk mounting portionwith a cylindrical outer circumferential surface. The hub is preferablyimpact extruded or cast and is pressed hot on to the magnetic yoke. Inprinciple, other possibilities for joining hub and yoke exist, such as abonding together of the two parts.

The magnetic yoke can have a cup or pot-shaped construction as is known.It is more advantageous, however, to provide an annular magnetic yokeand appropriately insert a magnetic shield ring in the hub extendingradially inwardly substantially from the clean chamber axial end of theannular magnetic yoke. As a result, necessary guidance of the magneticflux and efficient magnetic shielding of the storage disks with respectto the drive motor are achieved. The combination of yoke ring and shieldring can be produced less expensively than a cup or pot. The shield ringcan be relatively thin so that the overall axial size of the drive canbe further reduced, or, for a constant axial size, provide more spacefor a hub end wall at the closed end of the subassembly comprising thehub, magnetic yoke and motor magnet. The magnetic yoke can beappropriately constructed as a rolled ring, particularly a steel ring,or as a portion of a tube.

The rotor and the hub can be fixed to a shaft which is supported in abearing system at least partly housed within the drive motor stator. Abearing bush receiving the shaft can be shaped on to the yoke, if theyoke is constructed in cup-shaped manner, or preferably on to the hub.This obviates a separate component of the bush. The rotor and the hubcan, according to a modified construction, be mounted to rotate togethervia a bearing system of a fixed shaft, the leads of the stator windingpassing through the fixed shaft to the outside of the drive.

A control magnet, for example, in the form of a control magnet ring, ispreferably connected to the unit that includes the rotor and the hub,the magnet interacting with a stationary magnetic field-sensitiverotation position sensor whose function is to produce commutatingcontrol signals and optionally additional control signals, such as apulse for a given rotor reference position. The control magnet isappropriately located on the axially open side of the unit that includesthe rotor and hub. It can be axially aligned with the rotor magnet. Therotor magnet can optionally serve as the control magnet. The rotationposition sensor is advantageously placed on a printed circuit boardaxially facing the axially open side of the unit comprising the rotorand hub.

In FIGS. 5 and 6, the drive motor 118 has a stator 119 with a statorlamination bundle 110. The bundle 110 is radially symmetrical withrespect to a central rotation axis 110A and is provided with an annularcentral portion 110B. The stator laminations 110 form six stator poles111A to 111F, each of which, in the plan view according to FIG. 5 has asubstantially T-shaped configuration. The stator poles are positionedwith a reciprocal angular distance of 60°. A sintered iron core can beprovided in place of a bundle of laminations. Pole shoes 112A to 112F ofthe stator poles together with a permanent magnetic motor magnet 113define a substantially cylindrical air gap 114. In the manner indicatedin FIG. 5, motor magnet 113 is radially magnetized in quadripolar mannerin the circumferential direction, that is, it has four portions 113A to113D and on the inside of the annular motor magnet 113 facing the airgap 114 are provided in alternating sequence two magnetic north polesand two magnetic south poles 115, 116. In the illustrated embodiment,each of the poles 115 and 116 have a width of substantially 180° e1,(corresponding to 90° mechanical). Thus, an approximately rectangular ortrapezoidal magnetization is obtained in the circumferential directionof the air gap 114.

The motor magnet 113 is fitted in a soft magnetic material externalrotor cup or pot 117 serving as a magnetic yoke and has a magneticshield bonded thereinto. The cup 117 and the magnet 113 together form anexternal rotor 130. The external rotor cup 117 has an end wall 117A(FIG. 6) and a cylindrical circumferential wall 117B. The motor magnet113 can be a rubber magnet, or a plastic-bonded magnet. In place of aone-part magnet ring, dish-shaped magnet segments can be bonded or insome other way fixed into the cup 117. Particularly suitable materialsfor the magnet ring or segments are magnetic material in a syntheticbinder, a mixture of hard ferrite and elastomeric material, ceramicmagnetic material or samarium cobalt.

While in the represented embodiment each of the poles extends oversubstantially 180° e1, it is also possible to work with narrower poles.The rotor pole width, however, should be at least 120° e1 to obtain ahigh motor output.

Together the stator poles 111A to 111F define six stator slots 120A to120F, in which is placed a three-strand stator winding. Each of thethree strands includes two 120° e1-cored coils 121,122; 123,124; and125,126. Each is wound around one of the stator poles 111A to 111F. Thetwo coils in series of each strand diametrically face one another, asshown in FIG. 5. The coils are preferably wound in bifilar manner (notshown). As can be gathered from the diagrammatic representation of FIG.5, any overlap between coils 121 to 126 is avoided and in this wayparticularly short coil winding heads 127 (FIG. 6) are obtained. Theslot openings 128A to 128F can be between 3° e1 and 30° e1. In thepresent stator winding configuration, slots 120A to 120F can beexcellently filled. There is generally no need to provide caps for theslot openings 128A to 128F.

The present motor design makes it possible to obtain a relatively largehole 129 within the stator, because the depth of the stator slots 120Ato 120F can be kept relatively small. It is easy to obtain ratiosbetween the diameter I of internal hole 129 and the stator externaldiameter E of the pole shoes 112 of at least 0.35. Preferably, the I/Evalue is in the range 0.4 to 0.7. The L/E ratio between the axial lengthL (FIG. 6) of the stator iron and the stator external diameter E ispreferably equal to or smaller than 1. These dimensioning ratios are ofparticular significance in connection with a stable mounting of therotor. This is of particular importance in connection with drives fordisk storage systems. In addition, the overall resistance of the statorwinding is kept particularly small.

For the purpose of the mounting of the rotor 130, according to FIG. 6 inthe center of the external rotor cup 117 is fixed a stub shaft 132 via abearing bush 131 shaped on to the cup, the shaft being supported viaaxially spaced ball bearings 133 in a cylindrical sleeve 134, which alsocarries the stator laminations 110 and is fixed to an assembly flange135.

A preferably light metal hub 137 (FIG. 6) for a rigid disk is providedwith a cylindrical disk mounting portion 136 and is placed, for example,by shrinking onto the external rotor cup 117. One or more rigid storagedisks 139, preferably magnetic disks, are placed on the disk mountingportion 136. The disk mounting portion extends through a central opening140 in the storage disks 139, which are reciprocally axially spaced byspacers 141 and are fixed with respect to the hub 137 by a knownclamping device. In the embodiment shown in FIG. 6, somewhat more than2/3 of the axial dimension of the magnetically active stator and rotorparts of drive motor 118, that is, the motor magnet 113 and the statorwindings 121 to 126 project into a space or volume 146 surrounded by thedisk mounting portion 136. The wall thickness of the disk mountingportion 136 of the hub 137 is smaller than the wall thickness of thecylindrical circumferential wall 117B of the cup 111 that forms themagnetic yoke, so that a maximum cross section is made available for therotor parts 113, 117, 119 in the predetermined central opening 140. Inparticular, the wall thickness of the disk support portion 136 is madeas small as possible consistent with mechanical strength requirements.To increase the dimensional stability of the hub 137, near the open endof the unit that includes the hub 137, the external rotor cup 117 andthe motor magnet 113, the hub carries a thickened, outwardly radiallyprojecting flange 147, which simultaneously axially supports the rigidstorage disk 139 closest to the flange.

The hub 137, together with the storage disks 139 supported thereon, islocated in a clean chamber 149, defined by the disk storage casingparts. The assembly flange 135 forms part of the clean chamber boundarytowards the lower side in FIG. 6. The upper bearing 133 in FIG. 6 islocated between a shoulder 151 on the sleeve 134 and a spacing ring 152,whose side remote from the bearing 133 engages the bottom surface of thebearing bush 131. The stub shaft 132 is convex at its lower end 153 andis appropriately mounted in an axial bearing (not shown). Close to thelower end 153, a fastening ring 155 is arranged in an annular slot 154of the shaft 132. Against the upper surface of the ring bear two cupsprings 156, which engage on an intermediate ring 157. The lower ballbearing 153 is positioned between the intermediate ring 157 and afurther shoulder 158 of the sleeve 134.

The assembly flange 135 carries a circuit board 138, which canoptionally carry the commutating electronics and/or other circuitcomponents, such as for speed regulation. The circuit board 130 moreparticularly carries three rotation position sensors 142, 143, 144. Inthe illustrated embodiment, they are magentic field sensors, such asHall generators, field plates, magnetic diodes and the like.Bistable-switching Hall IC's are particularly advantageous. The use of180° e1 wide rotor poles 115, 116 makes it possible to use the motormagnet 113 as the control magnet for the position sensors 142, 143, 144.The embodiment according to FIG. 6 shows the rotation position sensors142, 143, 144 (of which only sensor 142 is seen) axially facing themagnet 113 controlling them. It is also possible to arrange the rotationposition sensors in the manner indicated in broken line form in FIG. 6to radially face the magnet 113 controlling them. The rotation positionsensors 142, 143, 144 are appropriately so peripherally positioned withrespect to the coils 121 to 126 that changes to the sensor switchingstates substantially coincide with the zero crossings of the associatedcoil voltages. In the embodiment according to FIG. 5 this is achieved inthat the rotation position sensors are displaced by 15° mechanical withrespect to the center of the slot openings 128A, 128B, 128C.

The embodiment according to FIG. 7 essentially differs from thataccording to FIG. 6 in that a control magnet 145 separate from the motormagnet 113 is provided for energizing the rotation position sensors 142,143, 144. The control magnet 145 is located radially outside the motormagnet 113 on the bottom of a flange 117C, which projects radiallyoutwardly from the peripheral wall 117B of the external rotor cup 117,on its open end. The external rotor cup 117 and the hub 137' terminatein a flush manner at the open end in the embodiment of FIG. 7. At 159 isindicated a connection of one of the coils 121, 126 to a contact of theprinted circuit board 138 which extends outwardly through an opening 161in the assembly flange 135, a connecting cable 160.

FIG. 8 illustrates another embodiment of the disk storage drive inwhich, differing from the embodiment of FIG. 6 and 7, a hub 164corresponding to the hub 137 has an end wall 164A engaging the end wall117B of the external rotor cup 117. A bearing bush 165 for the shaft 132is formed integrally in the end wall 164A. On the end of the disksupport portion 166 of the hub 164 remote from the end wall 164A islocated a radially outwardly bent flange 167, which passes into acircumferential wall 168 concentric to, but having a larger diameterthan the disk mounting portion 166. Radially outwardly bent flange 167and circumferential wall 168 together comprise a disk support shoulderthat is disposed substantially completely within a recess 189 ofassembly flange 183. A sidewall 192 of recess 189 parallelscircumferential wall 168. Assembly flange 183 has a flat portion 193that extends radially outside of the recess 189. The circumferentialwall 168 engages radially and externally over the flange 117C of the cup117. The junction between the flange 117C and the circumferential wall168 is sealed in the manner indicated at 169 by varnish, adhesive or thelike. Thus, as in FIG. 7, it is ensured that dirt particles are notpassed radially outwardly from the flange 117C and from the recess 189of assembly flange 183 into the clean chamber 149. The control magnet145 interacting with the rotation position sensors (of which only sensor142 is shown in FIG. 8) is axially aligned with the motor magnet 113 andis fitted to the side of the magnet 113 remote from the end wall 117A.The external rotor cup 117 is drawn down into the recess 189 of flange183 to such an extent in FIG. 8 that it surrounds the control magnet145. The space left free between the end wall 117A and the end of themagnet 113 facing the wall is filled with an adhesive or some otherfilling material 170. The bearing system for the shaft 132 formed by thetwo ball bearings 133 is sealed with respect to the inner area of themotor and consequently with respect to the clean chamber 149 by means ofa magnetic fluid seal 172, which comprises two annular pole pieces 173,174, a permanent magnet ring 175 located between these pole pieces and amagnetic fluid (not shown), which fluid is introduced into an annularclearance 176 between the magnet ring 175 and a portion 177 of the shaft132. Seals of this type are known as "ferro-fluidic seals". The seal 172effectively prevents the passage of dust particles from the bearingsystem into the clean chamber 149. The seal 172 is adjacent to, butaxially spaced from, the bearing bush 165, which ensures that magneticfluid is not drawn by capillary action out of the seal 172.

As can be gathered from FIG. 8, the magnetically active stator and rotorparts are substantially completely housed within the space enclosed bythe disk support portion 166. FIG. 8 also shows an axial bearing 179 forthe shaft 132. The bearing 179 is located on a spring clip 180, which isin turn placed on a cover 181 introduced into the end of a sleeve 182remote from the clean chamber 49. Similarly to the sleeve 134 of theembodiment according to FIGS. 6 and 7, the sleeve 182 receives thebearings 133, but is connected in one piece with the assembly flange 183corresponding to the assembly flange 135.

Similarly to the spring clip 180, the axial bearing 179 is preferablyelectrically conducting. This makes possible the elimination ofelectrostatic charges of the shaft 132 via the bearing 179 in the springclip 180.

The circuit board 138 is connected to the assembly flange 183 in therecess 189 via an adhesive coating 184, which is located in a slot 185in the recess 189 of the assembly flange 183. To further reduce theoverall axial height of the disk storage drives, the circuit board 138is provided with openings 186 in the vicinity of the rotation positionsensors, and the rotation position sensors are introduced into the slot185 and the openings 186. Near the engagement point between the upperpole piece 173 and the inner circumferential wall 187 of the sleeve 182,an additional seal by means of coating lacquer or the like is providedat 188.

The embodiment according to FIG. 9 is similar to that of FIG. 8. Thebearing bush 131, however, is formed integrally in the end wall 117A ofthe external rotor cup 117, which acts as a magnetic shield. The endwall 117A contains three threaded holes 190, which are circumferentiallydisplaced from one another by 120°. The holes 190 are used for fittingthe earlier mentioned but not shown clamping device for the rigidstorage disks 139 (FIG. 6). Under the end wall 117A is located a coverring 191 which seals the inner area of the motor relative to the cleanchamber 149 near the threaded holes 190. Most of the axial length of themagnetically active stator and rotor parts of the drive motor are onceagain located in the area 146, which is surrounded by the disk supportportion 136' of the hub 137' similar to that shown in FIG. 7.

FIG. 10 shows a further modified embodiment of the invention, whichessentially differs from the previous constructions of FIGS. 5-9 in thatthe external rotor cup 117 is replaced by a soft magnetic yoke ring 194and a separate soft magnetic shield ring 195. The shield ring 195extends from the clean chamber-side axial end 196 of the yoke ring 194in a radially inwardly direction. The wall thickness of the shield ring195 can be much less than that of the yoke ring 194. Threaded holes 197functionally corresponding to the threaded holes 190 of FIG. 9 areformed in the end wall 198 of a hub 199, in which integrally is formedthe beating bush 1100 for the shaft 132. Near the threaded holes 197, ashield ring 195 is provided with depressions 1101, which depressionspermit the use of the full thread length of the threaded holes 197.Filling material 170 is provided in the space between the upper end ofthe motor magnet 113 in FIG. 10, the end 196 of the yoke 194 and theradially outer part of the shield ring 195. The magnetically activerotor and stator parts are more than 2/3 located in the area surroundedby the cylindrical disk support portion 1102 of the hub 199.

The yoke ring 194 can be a rolled ring, particularly a steel ring, or aportion of a tube. Manufacture is simplified compared with the use of anexternal rotor cup 117. In addition, additional axial length is saved,because on the one hand the wall thickness of the shield ring 195 can bekept small, and because on the other hand no space is lost, consideringthe way in which some space is required when using the cup 117 with itsradius r (FIG. 9) at the transition point between its circumferentialwall 117B and its end wall 117A. The axial construction space which thushas been made available can be used to give the and wall 198 a greaterthickness and consequently increase the length of the threaded holes197.

Whereas in the case of the embodiment according to FIGS. 5 to 10, theshaft 132 rotates in operation, FIGS. 11 and 12 illustrate embodimentswith a stationary shaft 1105. According to FIG. 11, the shaft 1105 isfitted into the disk storage device. By means of the first ball bearing1106, a hub 1107 is mounted on shaft 1105 to rotate therewith. The hub1107 has an end wall 1108 with a formed-in bearing bush 1109, a disksupport portion 1110 and, on the side remote from end wall 1108, aradially outwardly projecting reinforcing flange 1111. The hub 1107 isconnected to a soft magnetic yoke ring 194. The soft magnetic shieldring 195 engages the inside of the end wall 1108. The circuit board 138with the rotation position sensors, of which only the sensor 142 isshown in FIG. 11, is suspended by means of supports 1112 (FIG. 12) onthe stator laminations 110. motor cover 1114 is mounted by means of asecond ball bearing 1113 on the shaft 1105, the cover tightly sealingthe motor on the axial end remote from the end wall 1108. A magneticfluid or ferrofluidic seal 172 or 172' discussed in detail relative toFIG. 8, is provided on each of the outside of the bearings 1106, 1113.The seals 172, 172' ensure a sealing of the bearing system with respectto the clean chamber 149, so that the complete drive motor can belocated in the clean chamber. The connections of the stator windingand/or the electronic components mounted on the circuit board 138 can beled out by means of a cable 1115, which is placed in an axial slot 1116of the shaft 1105.

The embodiment of FIG. 12 differs from that of FIG. 11 substantially inthat in place of the shield ring 195 and the yoke ring 194 there is aone-piece soft magnetic material cup 1117 with an end wall 1117A and acircumferential wall 1117B corresponding to the cup 117.

In the embodiments according to FIGS. 11 and 12, the magnetically activestator and rotor parts of the drive motor are located within the areasurrounded by the disk mounting portion 1110.

It should be apparent that certain constructional features areinterchangeable in all the illustrated embodiments.

What is claimed is:
 1. A spin motor for rotating a storage disk in adisk storage device, comprising:a stator and a winding on said stator;an external rotor coaxially surrounding said stator and spaced therefromby a substantially cylindrical air gap, said rotor having a permanentmagnetic rotor magnet and a soft magnetic yoke, and a hub concentric tosaid yoke, said hub being connected to the rotor for rotation therewithand having a cylindrical disk support portion which can pass through acentral opening of a storage disk for receiving at least one storagedisk, said hub having an outwardly radially projecting flange at oneaxial extremity of said rotor; and a support member contiguous with thedisk storage device for supporting said stator, said support memberincluding a radially extending flange adjacent said axial extremity ofsaid rotor, said support member flange having a recess cooperating withsaid outwardly radially projecting flange of said hub to allow saidoutwardly radially projecting flange to nest in said recess, therebymaking the motor more compact.
 2. The spin motor for rotating a storagedisk in a disk drive according to claim 1, wherein at least part of theaxial extent of said outwardly radially projecting flange of said hub isreceived within said recess.
 3. The spin motor for rotating a storagedisk in a disk drive according to claim 1, wherein said soft magneticyoke has an outwardly radially projecting flange adjacent said outwardlyradially projecting flange of said hub, and wherein said support memberflange has a recess cooperating with said outwardly radially projectingflange of said yoke.
 4. The spin motor for rotating a storage disk in adisk drive according to claim 3, wherein said soft magnetic yoke has anoutwardly radially projecting flange adjacent said outwardly radiallyprojecting flange of said hub, said outwardly radially projecting flangeof said yoke being at least partly within said cooperating recess. 5.The spin motor for rotating a storage disk in a disk drive according toclaim 3, wherein said flange of said hub has a circumferential wall thatengages radially and externally over said flange of said yoke.
 6. Thespin motor for rotating a storage disk in a disk drive according toclaim 3, wherein said recess cooperating with said flange of said hub iscommon with said recess cooperating with said flange of said yoke. 7.The spin motor for rotating a storage disk in a disk drive according toclaim 1, wherein two recesses are formed in said support member flangeand define a stepped surface in said support member flange.
 8. The spinmotor for rotating a storage disk in a disk drive according to claim 1,further comprising a bearing tube fixed to said support member flange.9. The spin motor for rotating a storage disk in a disk drive accordingto claim 1, wherein the hub is composed of a material that is suitableafter machining for clean area use.
 10. The spin motor for rotating astorage disk in a disk drive according to claim 9, wherein said materialis aluminum.
 11. The spin motor for rotating a storage disk in a diskdrive according to claim 9, wherein the external circumferential surfaceof the disk support portion has a machined finish.
 12. The spin motorfor rotating a storage disk in a disk drive according to claim 1,wherein the external circumferential surface of the disk support portionis formed without removal of material.
 13. The spin motor for rotating astorage disk in a disk drive according to claim 1, wherein the externalcircumferential surface of the disk support portion is extruded or cast.14. The spin motor for rotating a storage disk in a disk drive accordingto claim 13, wherein said hub is pressed hot onto said magnetic yoke.15. The spin motor for rotating a storage disk in a disk drive accordingto claim 1, further comprising:a control member mounted beneath saidflange at the axial extremity of the rotor; and a sensor mounted on aprinted circuit board on said support member for sensing the passage ofsaid control member to provide a rotation control signal.
 16. A spinmotor for rotating a storage disk in a disk drive according to claim 15,wherein said printed circuit board is received within a recess in saidsupport member flange.